There has conventionally been provided a drum type washing machine including a water tub which is elastically supported by suspensions each mounted on a bottom plate of an outer casing. Each suspension includes a damper absorbing vibration of a drum which is located in the water tub, accommodates laundry and is then rotated and therefore vibration of the water tub. As this type of damper, one which is known employs as an operating fluid a magnetic viscous fluid (MR fluid) changing its viscosity according to the intensity of magnetic field.
The damper employing the magnetic viscous fluid includes a cylinder enclosing a bobbin on which a coil is wound and two yokes mounted on both ends of the bobbin respectively. The damper further includes a shaft which is inserted into the cylinder so as to be axially reciprocable relative to the bobbin and the yokes. The magnetic viscous fluid fills a space defined between the shaft and the bobbin and yokes in the cylinder.
In the above-described construction, a seal is provided between the shaft and the yokes to prevent the magnetic viscous fluid from leaking. However, when dimensional precision and assembly precision of components of the bobbin and each yoke are reduced in fixing the yokes to the respective ends of the bobbin, gaps occur between the bobbin and the yokes. There is a possibility that the magnetic viscous fluid may bypass the seal through the gaps thereby to leak within the cylinder. Furthermore, when fixation of the bobbin and the yokes to the cylinder becomes insufficient, there is a possibility of reduction in a vibration damping force and variations in the characteristics.